Electroless deposits of nickel-phosphorous are well-known and widely utilized in various industries as functional coating over a variety of substrates. Solutions used to produce these deposits are versatile and well-known. In many cases, however, it is useful to deposit other types of metals over nickel-phosphorous surfaces in order to obtain certain desirable properties such as corrosion resistance, contact reliability, improved conductance, or solderability. In attempting to accomplish this, artisans have found that nickel-phosphorous surfaces, particularly those with relatively high proportions of phosphorous, are not catalytic for initiation of many conventional electroless plating baths including, without limitation, electroless copper/formaldehyde, electroless gold, electroless palladium, electroless cobalt, and in some cases, other electroless nickel-phosphorous baths.
It is well documented in the art, that nickel-phosphorous surfaces can be non-catalytic to the initiation of various subsequent electroless plating solutions. In the prior art, various procedures have been utilized to render such non-catalytic surfaces catalytic. Typical procedures known for activation of non catalytic nickel-phosphorous surfaces include activation with precious metal catalysts, such as palladium, zincating, impressing of favorable galvanic potentials and others. U.S. Pat. No. 4,181,760 (Feldstein), incorporated herein in its entirety by reference, teaches the activation of non-catalytic nickel-phosphorous surfaces with an electroless nickel-boron pre-plate. It is also well documented, however, that such prior art activation procedures are tedious and costly. The present invention addresses the needs of the art and overcomes many of the shortcomings of the prior teachings.